WASHINGTON (CNN) -- President Bush has approved the Army's request to execute a soldier convicted of rape and murder, the White House announced Monday evening.

Pvt. Ronald Gray, seen here in 1988, has been on the military's death row for 20 years.

Pvt. Ronald Gray has been on the military's death row at Fort Leavenworth, Kansas, since 1988. His execution would be the first for the U.S. military since 1961, but the White House said it expects further appeals before the sentence is carried out.

"While approving a sentence of death for a member of our armed services is a serious and difficult decision for a commander-in-chief, the president believes the facts of this case leave no doubt that the sentence is just and warranted," White House spokeswoman Dana Perino said.

Gray was convicted of raping and killing a female Army private and a civilian near his post at Fort Bragg, North Carolina. He was also convicted of the rape and attempted murder of another fellow soldier in her barracks at Fort Bragg.

"The president's thoughts and prayers are with the victims of these heinous crimes and their families and all others affected," Perino said.

Both military and civilian courts found Gray responsible for the crimes committed between April 1986 and January 1987. Gray pleaded guilty to two murders and five rapes in a civilian court and was sentenced to three consecutive and five concurrent life terms.

A general court-martial at the Army's Fort Bragg then tried him and in April 1988 convicted him of two murders, an attempted murder and three rapes. He was unanimously sentenced to death.

Members of the U.S. military have been executed throughout history, but just 10 have been executed with presidential approval since 1951 under the Uniform Code of Military Justice, the military's modern-day legal system.

Military courts have not yet set an execution date for Gray, who can still appeal through civilian federal courts. The Army also has sought Bush's authorization to execute another condemned soldier, Pvt. Dwight Loving, who was convicted of killing and robbing two cab drivers in 1988.

The last U.S. military execution was in 1961, when Army private John Bennett was hanged for raping and attempting to kill an 11-year-old Austrian girl. Bennett was sentenced in 1955. The U.S. military hasn't actively pursued an execution for a military prisoner since President John F. Kennedy commuted a death sentence in 1962.

Six men are currently on military death row.

Bush allowed 152 executions as governor of Texas and has signed off on three executions of federal inmates since he became president -- including that of Oklahoma City bomber Timothy McVeigh, who was put to death in 2001.